Steam literally always has stuff on sale, and they run 3-4 huge sales every year.
Or check out Epic. They have a much smaller catalog, but they give out 1 or 2 free games every week. And usually a week or two before Steam runs one of their big sales Epic runs one, during which they give out a free game every day. They also run coupon boosted sales a couple times a year that let you take an additional $10 after the sale price. The free games are usually some weird indie game, but from time to time they give a big name title. About a month ago they gave out Borderlands 3 for free. I've got about 140 games on Epic, have only paid for about 15 of them.